The Oklahoma Supreme Court on Friday struck down the state's proposed personhood ballot question, deeming that the legislation -- which would have declared that life begins at conception -- is clearly unconstitutional.

The unanimous ruiling by the nine-member court came after the state Legislature failed to pass The Oklahoma Personhood Act. Although the bill, which would have granted fertilized embryos the same rights as living human beings, sailed through the Senate, it failed in the House before reaching a vote.

In its ruling, the Oklahoma Supreme Court ruled enacting the personhood bill would violate the U.S. Supreme Court's 1992 decision in Planned Parenthood v. Casey, which allows states to pass some abortion restrictions but prevents them from overturning the constitutionally protected right to terminate a pregnancy.

The mandate of Casey is as binding on this Court today as it was twenty years ago, the court wrote in its decision. Initiative Petition No. 395 conflicts with Casey and is void on its face and it is hereby ordered stricken.

The American Civil Liberties Union and the Center for Reproductive Rights filed a protest with the state Supreme Court on behalf of several Oklahoma doctors and residents, arguing the measure would violate women's privacy and likely completely outlaw abortion across the state. Opponents also argue the proposal would have interfered with women's right to use certain forms of contraception and medical procedures such as in vitro fertilization.

Similar personhood bills have been introduced in several states, to almost no avail. In November, a personhood ballot measure failed in Mississippi, widely considered to be the most conservative state in the nation; a similar proposal was also put on hold by the Virginia Legislature until next year.

As of now, Missouri is the only state to have a personhood law on the books.